Fix a recursion in mxm send flow which happens when mpi starts a new send from the context of send completion callback.

cmr=v1.7.5:reviewer=jsquyres

This commit was SVN r30265.

ompi/mca/mtl/mxm/mtl_mxm_send.c

@@ -201,8 +201,12 @@ int ompi_mtl_mxm_isend(struct mca_mtl_base_module_t* mtl,
     if (mode == MCA_PML_BASE_SEND_SYNCHRONOUS) {
         mxm_send_req->base.flags           |= MXM_REQ_FLAG_SEND_SYNC;
     } 
+#else
+#if defined(MXM_REQ_SEND_FLAG_REENTRANT)
+    mxm_send_req->flags                    = MXM_REQ_SEND_FLAG_REENTRANT;
 #else
     mxm_send_req->flags                    = 0;
+#endif
     if (mode == MCA_PML_BASE_SEND_SYNCHRONOUS) {
         mxm_send_req->opcode               = MXM_REQ_OP_SEND_SYNC;
     } else {